This invention relates to a stored program type control system utilizing a micro-processor.
A prior art control system of the type referred to above has been fabricated with integrated circuits such as a TTL (transistor-transistor logic) and considered as a mini-computer which is used exclusively to act as a sequence controller for efficiently executing a sequence. As a result of recent advances in semiconductor techniques, however, a microprocessor fabricated using LSI techniques was developed which is extremely advantageous from the standpoint of cost and reliability. In a sequence controller, it is necessary to use universal instruction words which are utilized in a micro-processor in view of the requirements for improving the data transmission function and self-detection of faults.
For this reason, it has been the practice to use both universal instruction words and sequence instruction words making it desirable (1) to use a program written with universal instruction words, without any modification, and (2) to execute an interruption processing program with either the universal instruction words or the sequence instruction words and to return to the original instruction words when the execution of the interruption processing program is completed.